2.0 - 2.7 conversion

[Project_E30]

Correct! This is the cheap, easy, quick 2.7 conversion that can be done in a few hours. 2.7 zone chip is the one for the job.

So there is no need for cam adjustment then?

[whipsey]

so what sort of bhp are u expecting when the engines built ?

[blingsta]

well my 2.5 has a few bolt on xtras and is pushing 176bhp at the moment, im in the process of doing the 2.7 conversion too and i will be dissapointed if i lose any bhp. im hoping for at least 190 bhp

[Chaos]

Argos from what you said this swap differs very much from UK models to US models

It will be in the US because

a) The US Eta is low compression (well, 9:1)

b) You don't have any 731 head castings over there.

You need to be talking to JonB here on the Zone to get some 731 heads crated over to the States. You'd need the complete head with cam and inlet manifold as a bolt on power increase. You'd go from 129 to 170 bhp instantly.

As for chips, you will ALWAYS need one. It's not just about fuelling (btw you will need a set of 325i injectors with a 2.7 - 2 litre ones aren't good enough). The other big thing is ignition timing. Don't forget that when you increase the stroke of an engine, the piston speeds increase also and going from a 2 litre to a 2.7 is a massive jump in terms of ignition timing.

In other words:

at 5000 rpm the piston speed of a 2 litre is about 36 ft per sec. A 2.7 is around 44 feet per sec so you can see how the ignition advance in a 2 litre ECU is going to be totally wrong for a 2.7! Just upping the fuelling is not enough and it needs to be spot on. Too little advance and it'll just feel flat, too much low speed advance and the crank will rumble like buggery and eventually hole a piston.

I'm trying to get a copy made of an old AMD chip that was custom made on a dyno for an original C2 2.7 Alpina.

So just to confirm. If we go the 731 head route the only thing me need to change regarding timing would be to get a suitable chip fitted to the ECU? Maybe the one from the zone shop?

Other than that we can use all the mechanicals from a 525e bottom end and a 731 cast head and suitable e30 sump.


Cheers

that post of andys is aimed at the american guy m8.

why wud u wanna use a 731 head here, when its been proven that u can use the better (bigger ports, bigger valves, better cam) 885 head from a 325i

[blingsta]

theres still the doubt in my mind regarding compression!, is it better to use 320 head but port and use 325 valves or just slap the 325 head on and lose the higher compression that 320 would give you?

[madbuck]

i have a 2.7 engine and box the rpm tdc sensors are on the right side of the gear box, looking at the front of the car .?what type of gear box would that be.? would i have to change the front pulley to fit the 325 wiring and the ecu ?

[bottlecapE30]

Argos from what you said this swap differs very much from UK models to US models

It will be in the US because

a) The US Eta is low compression (well, 9:1)

b) You don't have any 731 head castings over there.

You need to be talking to JonB here on the Zone to get some 731 heads crated over to the States. You'd need the complete head with cam and inlet manifold as a bolt on power increase. You'd go from 129 to 170 bhp instantly.

As for chips, you will ALWAYS need one. It's not just about fuelling (btw you will need a set of 325i injectors with a 2.7 - 2 litre ones aren't good enough). The other big thing is ignition timing. Don't forget that when you increase the stroke of an engine, the piston speeds increase also and going from a 2 litre to a 2.7 is a massive jump in terms of ignition timing.

In other words:

at 5000 rpm the piston speed of a 2 litre is about 36 ft per sec. A 2.7 is around 44 feet per sec so you can see how the ignition advance in a 2 litre ECU is going to be totally wrong for a 2.7! Just upping the fuelling is not enough and it needs to be spot on. Too little advance and it'll just feel flat, too much low speed advance and the crank will rumble like buggery and eventually hole a piston.

I'm trying to get a copy made of an old AMD chip that was custom made on a dyno for an original C2 2.7 Alpina.

I have already finished my 2.7l with post 88 pistons 325i head 19.25lbs injectors honed intake m30 amf 325i throttle body and ajust. fuel reg. ( sure i forgot some stuff) It makes just about 225 lbs feet and 210hp i need a new cam and some ECU tweeking to get the idle right. Thanks anyway for the info.

[WerkdE30]

hmm 2mm would be a fair bit or reduction i imagine. and the cam is different so combined im guessing thered be a substantial loss. the way im thinkin bout it is if im spendin the money on the head then ill go even bigger valves and lumpy cam. why use valves from a 2.5 ltr on a 2.7 when your whole aim is chasing power.

325i manifold has slightly smaller ports than 320i head on my car. . . i dont know why.

[Templ8e30]

hmm 2mm would be a fair bit or reduction i imagine. and the cam is different so combined im guessing thered be a substantial loss. the way im thinkin bout it is if im spendin the money on the head then ill go even bigger valves and lumpy cam. why use valves from a 2.5 ltr on a 2.7 when your whole aim is chasing power.

325i manifold has slightly smaller ports than 320i head on my car. . . i dont know why.

I agree, 2mm extra is a substantial amount of airflow. I'd avoid even bigger valves combined with a lumpy cam for fear of clattering the pistons, the machined 'pocket' in the piston is designed for a specific size of valve and going too far will cause problems.

I noticed the port thing too, my spare 731 head has bigger ports than the 885 head i used to have. The 885 has a flat roof to the inlet ports whereas the 731 has a rounded roof and seems to be bigger all round

Cheers,

Iain T

[blingsta]

right then!! definately back to my original plan of modding the 320 head.. ive been quoted £60 by machine shop to re-seat 2.5 valves in 320 head and from what i believe the cam on a 325 will fit a 320 head, so sounds more beneficial to keep compression, and port 320 head a little..

[Templ8e30]

Man that's cheap - have you got their number? £60 for around 2 days work - is it in Poland??
It's not about 'reseating valves'. It's about removing the old valve seats, machining out all 12 seat recesses in the head (around 6-7 hours), pressing in twelve new valve seats, machining 12 new valve seats and then a few hours with a grindstone opening out the throats around the valve seats.

Sixty quid. Wow. The number please!!!

It doesn't take 7 hours to machine the seat recesses in the head, 2 at the most.

My Engine builder has quoted me £130 to skim the head and fit and machine 12 new larger seats. I'll be doing the porting work myself as he's not keen on doing this.

I agree £60 is way too cheap but it isn't a massive job to fit bigger seats.

If I didn't lose 10% compression and good 325i heads were plentiful and cheap I'd use one but they aren't so I won't

Cheers,

Iain T

[Project_E30]

Correct! This is the cheap, easy, quick 2.7 conversion that can be done in a few hours. 2.7 zone chip is the one for the job.

So there is no need for cam adjustment then?

So is there any need for cam adjustment?

[Brianmoooore]

Correct! This is the cheap, easy, quick 2.7 conversion that can be done in a few hours. 2.7 zone chip is the one for the job.

So there is no need for cam adjustment then?

So is there any need for cam adjustment?

None at all.

[Project_E30]

Cheers

[blingsta]

Although i know the 325 head goes straight on, i think i'll im going to stick with 320 head and get the 325 valves to go on, also ask if they can port the intake too.. After much research, i think performance wise this will be best option..

[julianm40]

Hmmmm, this seems like a very good idea for me to do eventually. Is there anyone that regulaly does this for other people? You know what I mean...

[oze30]

So what year model 525 am I looking for?

[323i_rare]

I have a 1984 prefacelift 323i, apparently its the baby 325i. How would my head do if it is bolted onto the 525e bottom end, the same as the 325i would??

Sorry for barging in here, thanks.

[Jhonno]

323i head is the same as a 320i head

[kgb325]

Do the rods on a 525e handle 6000 rpm in a 2.7 [320head conversion]